U.S. Pat. No. 4,105,776, issued Aug. 8, 1978, describes a group of thioalkanoyl derivatives of azetidine-, or pyrrolidine- and piperidinecarboxylic acid compounds having the structural formula ##STR3## wherein the symbols can be, inter alia, as follows: R.sub.a can be hydrogen, lower alkyl, phenyl, substituted phenyl, phenyl-lower alkyl, ##STR4## or phenyl-lower ##STR5## R.sub.b can be hydrogen, R.sub.c can be hydrogen or lower alkyl, R.sub.d can be hydrogen, hydroxy or lower alkyl, R.sub.e can be hydroxy, --NH.sub.2 or lower alkoxy, n can be 0, 1 or 2 and m can be 1, 2 or 3.
U.S. Pat. No. 4,129,566, issued Dec. 12, 1978, describes derivatives of dehydrocyclicimino acids having the structural formula ##STR6## wherein the symbols can be, inter alia, as follows: R.sub.c, R.sub.f and R.sub.g can each be hydrogen or lower alkyl and n can be 0 or 1.
Belgian Pat. No. 861,454, published June 2, 1978, describes compounds having the structural formula ##STR7## wherein the symbols can be, inter alia as follows: R.sub.h can be hydrogen, lower alkanoyl or benzoyl, R.sub.i, R.sub.j and R.sub.k can each be hydrogen or lower alkyl, R.sub.L can be hydroxy or lower alkoxy, m can be 1, 2 or 3, n can be 0, 1 or 2 and m+n can be 2 or 3, p can be 0 or 1 and X can be O, S, SO or SO.sub.2, m being 2 and n being 1 when X is O.
The compounds set forth above are disclosed as being useful as inhibitors of the conversion of the decapeptide angiotensin I to angiotensin II, and are, therefore, useful in reducing or relieving angiotensin related hypertension.